TY - JOUR T1 - Cardiac shunt in COPD as a cause of severe hypoxaemia: probably not so uncommon after all JF - European Respiratory Journal JO - Eur Respir J SP - 960 LP - 962 DO - 10.1183/09031936.00058410 VL - 37 IS - 4 AU - B.G. Boerrigter AU - A. Boonstra AU - N. Westerhof AU - P.E. Postmus AU - A. Vonk-Noordegraaf Y1 - 2011/04/01 UR - http://erj.ersjournals.com/content/37/4/960.abstract N2 - To the Editors:Hypoxaemia is a common finding in chronic obstructive pulmonary disease (COPD) and may be aggravated during exercise. The main mechanism is perfusion through areas that are not well ventilated: a ventilation–perfusion mismatch. True shunting, defined as venous blood mixing directly with end-capillary blood at the arterial side of the circulation, is not a usual cause of hypoxaemia in COPD 1, 2. The amount of shunting related to ventilation–perfusion mismatch is usually made by the calculation of the shunt fraction while the patient is inhaling 100% oxygen. We present two cases of severe hypoxaemia in patients with COPD to show that a cardiac shunt can contribute to hypoxaemia, and that this shunt can be missed if the 100% oxygen method is used to quantify shunt.Patient A was a 68-yr-old man, referred from another hospital to our clinic for evaluation of severe dyspnoea and hypoxaemia. Patient complaints were rapidly progressive dyspnoea and severe impaired exercise tolerance with blue discoloration of the fingers and lips for 3 months. There were no complaints of coughing, sputum production or fever. Patient A ceased smoking 12 yrs previously after 60 pack-yrs. Physical examination revealed peripheral and central cyanosis, and a little ankle oedema. Arterial blood gas analysis revealed a hypoxaemia at rest, with an arterial oxygen tension (Pa,O2) of 42 mmHg and an arterial oxygen saturation (Sa,O2) of 77%. Pulmonary function tests showed moderate obstruction (forced expiratory volume in 1 s (FEV1) of 67% predicted and FEV1/synchronised vital capacity (SVC) ratio of 65% pred). Initiation of exercise resulted in immediate oxygen desaturation to 71%, preventing any further exercise. Radiological analysis by means of high-resolution computed tomography (CT), pulmonary angiography and ventilation–perfusion scan revealed only signs of emphysema. Transthoracic … ER -